1. Field of the Invention
The present invention is directed to a method and an apparatus for rotating caps on containers. The method and apparatus are primarily for use in container capping machines.
2. Description of the Prior Art
Bottle capping machines using the current art have been in existence for over 40 years. The current method for threadably capping bottles, utilizing driven rollers, may be seen in the applicant's In Line Capping Machine Model No. NEIL-C 46-16. The current roller technology advances a container along a predetermined path while gripping the container to prevent rotation. Two driven rollers are placed in a predetermined fixed position on opposing sides of the predetermined path so that each roller simultaneously engages the container cap as the container passes between the driven rollers. The rollers, being in a fixed position, engage the container cap tangentially to the predetermined path of the container. Thus, engagement of the cap by the rollers is for so short a period of time that the amount of rotation imparted to the cap of the container is severely limited.
As the rotation of the cap by these rollers is limited, a series of such pairs of rollers must be used to ensure sufficient total rotation to tighten the cap to the container. This is particularly true when the operation being supported is a capping operation, that is, from the initial engagement of the cap threads with the container threads to the final tightening, which may require several rotations of the cap. The number of pairs of rollers needed will depend upon a number of factors, including the amount of rotation of the cap required and the speed at which the containers are advanced. In a retorquing operation, where the cap is being retightened, the required rotation is small; however, a plurality of pairs of rollers is still needed to ensure proper tightening.
As required by customer specification, many bottle caps must be tightened to a predetermined torque. Due to the rapid movement of the containers and the short duration of time that the fixed rollers are engaged with the caps, it is difficult for a pneumatic friction clutch to obtain accurate torque measurements to ensure that the caps are threaded on the container tightly enough to meet predetermined torque requirements. Extra rollers may be required to ensure that sufficient torque has been applied. There is a need, therefore, for a method and an apparatus that implements the method that permits the rollers to maintain contact with the cap for a longer time period, reducing the number of rollers needed and improving the capability for torque measurement. Such a method will reduce the time for capping each container, increasing the productivity of the machine.